1. Field of the Invention
This invention relates to combustion engines, and particularly to a mechanism mountable on an engine for indicating when it is necessary to change the engine lubrication oil. The invention is applicable to various engines, including gas or diesel engines used in automobiles trucks, motor cycles and electric generators.
2. Prior Developments
Combustion engine life can be prolonged by periodically changing the engine lubrication oil. In many engine installations there is no convenient mechanism for knowing when to change the oil. In the case of automotive engines, usually the frequency between oil changes is measured in miles driven, e.g. five thousand miles in a typical situation. This system requires that the owner maintain a record of the odometer reading at a given oil change in order that he/she will know when to make next oil change. However, it is possible for the owner to misplace the record or otherwise forget the mileage at the last oil change. If the oil is inadvertently not changed at the desired frequency (e.g. every five thousand miles) the engine may tend to wear out prematurely.
Another problem associated with using the vehicle odometer reading as an indicator for the next anticipated oil change is the fact that the odometer reading may not accurately reflect the actual engine running time. For example, if the automotive vehicle is run primarily in urban areas the engine may be running at idle much of the time, e.g. when the vehicle is moving in stop-and-go traffic; in this case the odometer reading may be misleading. Also, if the driver tends to warm-up the engine for long periods of time prior to highway driving, the odometer reading will not fully reflect the engine running time. On the other hand, if most of the driving is done on super highways at elevated speeds the transmission may be in overdrive, in which case the odometer reading may give an excessively high indication of engine running time, or the odometer is not functioning, which frequently occurs in old cars.